VOL. LXIV.] PHILOSOPHICAL TRANSACTIONS. '' 543 



water, its martial and absorbent earths remain dissolved in it; as soon as this air 

 is separated from the water, in whole or in part, those earths, either in the whole 

 or in part, do also separate from it, and are no longer suspended in it, than 

 while they are united to a due proportion of this aerial solvent. Whence it 

 appears, that this mephitic air is the medium by which the metalline and absorbent 

 earths, contained in the Pouhon water, are held in solution ; and, contrary wise, 

 that those earths are the medium, by which this air is more firmly united to the 

 watery element in this compound, in which it enters as a principal ingredient, and, 

 by its solution in the water, and its union with these earthy substances, from a 

 very rare volatile and elastic body, is reduced to a fixed state. 



This dissolving power of mephitic air may further be proved from the recom- 

 position of the Pouhon water, by adding to it the air expelled from it by coction. 

 But as Mr. Cavendish has already shown, that the absorbent earths of Rathbone 

 Place water may be redissolved by the mephitic, or fixed air, which had been 

 extracted from that water; and as Mr. Lane has also demonstrated, that iron is 

 rendered soluble in water, by the medium of mephitic air. Dr. B. did not think 

 it necessary at that time to give an account of his experiments on the same 

 subject; but as those experiments contain some phenomena that have not yet 

 been noticed, he may perhaps offer them to the public on some future occasion. 



Schol. 1 . — From the foregoing experiments, it appears that the mephitic air 

 and martial earth, contained in the Pouhon waters, strongly attract each other, 

 and, uniting together, form a concrete soluble in water, and readily distinguished 

 in it, by the peculiarly brisk acidulous taste, which it receives from this aerial 

 principle, joined to a rough subastringent taste, which proceeds from the iron. 

 This concrete, like other vitriols of iron, strikes a black colour with galls, and 

 may well be esteemed a saline body of the neutral kind, of which the mephitic 

 air constitutes the spirituous solvent, and the martial earth its base. It further 

 appears, that the mephitic air is possessed of all the properties, by which some of 

 the chemists have distinguished those pure and simple bodies, or spirits, which 

 by them are esteemed, in their own nature, and of themselves, saline, and which, 

 in union with other bodies, form salts that are more compound. For this aerial 

 solvent, in like manner with the pure acid spirits, is soluble in water, and imparts 

 to it its peculiar sharp and acidulous savour: also, in combination with various 

 metalline and absorbent earths, this volatile elastic spirit, like those acids, forms 

 various saline concretes of the neutral kind ; inasmuch as those metalline and 

 absorbent earths, when united to this elastic spirit, are thus rendered soluble in 

 water ; and, in union with it, acquire peculiar savours, resulting in part from 

 this their spirituous principle, and in part also from the particular kind of earth 

 with which it is combined. This air therefore, considered in the relation which 

 it bears ot several earthy substances, and to water, considered also as it impresses 



